Process for manufacture of soluble coffee



Dec. 1, 1959 TEMPERATURE F.

W. P. CLINTON ETAL PROCESS FOR MANUFACTURE OF SOLUBLE COFFEE Filed June 27, 1956 T 2| I9 I8 I i, l7 l6 i l i g F F ll 1 1 J T I I l I --I5 -|4 -|3 -|a -|o l I I I g 23 I I g 32 3l 1 1 44 42 1 HEAT 151 L EXCHANGER coc JuNc. I I m N I 1 l SEC-HON HoT sec-now COLD SECTION PREFERRED UPPER LIMIT OF TEMPERATURE soo- PROFILE F05 aao- EXAMPLE I HOT/ SECTION 260- PREFERRED LOWER LIMIT OF TEMPERATURE LCOOLING sEcTIcm" HOT SECTION '-COL D SECTION-J COFFEE STAGES INVENTORS 772. #mu ATTORNEYS United States Patent PROCESS FOR MANUFACTURE or SOLUBLE [COFFEE William P. Clinton, Morris Plains, NJ., Herbert Guggenheim, Brooklyn, N.Y., and Theodore Kraut, Engie- Wood, and Roger M. Stinchfield, Mountain Lakes, Ni, assignors to General Foods Corporation, New York, N.Y., a corporation of Delaware Application June 27, 1956, Serial No. 594,132 6 Claims. (Cl. 99-71) This invention relates to a method of producing coffee extract in the form of syrup or dry soluble powder. More specifically it relates to an improved process by which it is possible to obtain high concentration of a concentrated coffee extract characterized by desirable flavor, taste, and aroma.

When ground roasted coifee is contacted with water, e.g. boiling water, to extract solubles therefrom at atmospheric pressure, it will be found that approximately 25% by weight of the original coffee will pass into solution. If the residual coifee grounds are then subjected to severe extraction conditions, i.e. higher temperatures and pressures, either with the same liquid or with fresh water, it will be found that approximately 23% more solubles may be extracted, making a total of about 48% extracted solubles. The additional 23% solubles may be considered coffee solids produced by hydrolysis or autoclaving and may include components having undesirable flavor. After this point has been reached, further attempts at extraction under still more severe temperature and pressure conditions, result in precipitation rather than solubilization and the total concentration of solubles formed drops rather than rises under these extended conditions. The 48% total extractvis characterized by low consumer acceptance because of its undesirable flavor, aroma and taste.

Instant or soluble coffee may be prepared commercially by passing water through a bed of ground roasted coffee in a percolator or extraction column. When feed water is passed through a single bed of coffee grounds,

the concentration of solubles in the extract is of a low order, usually only a few percent and accordingly it is necessary to pass this dilute extract through additional beds of coifee grounds in subsequent percolators to get higher concentrations of coffee in the extract liquor. The process is conducted semi-continuously in countercurrent manner so that fresh extracting liquor entering the system at one end is continuously concentrated as it contacts fresher coffee grounds in successive percolators. Each precolator is initially filled with a bed of fresh coffee grounds and when the content of solubles in the bed of the last stage has been lowered to the desired point, that percolator is disconnected from the system and spent coffee grounds withdrawn therefrom. Simultaneously a freshly filled percolator is placed on stream at the other end as the new first stage of the series of percolators, that percolatorvwhich formerly was the first stage now becoming the second stage, etc.

The stages of extraction are designated as coffee-stages, i.e., the stage wherein the most concentrated extraction liquor contacts fresh coffee grounds is designated the first coffee stage, and that wherein the fresh extraction liquor contacts substantially spent coffee grounds is designated the last coffee stage.

When solubles are extracted from the coffee bean by hot water according to prior art processes, the feed water is initially heated to as high a temperature as is possible I or desirableunder the conditions of operation, and ad-.

2,915,403 Patented Dec. 1, 1959 mitted to the last stage of a series of percolators. As the water passes through each percolator, its temperature drops and the temperature profile curve over the entire operation gradually slopes downwardly. This more-orless standard profile curve may be modified to some extent by increasing or decreasing the temperature of the feed water which raises or lowers the profile curve as it is customarily plotted in terms of temperature as the dependent variable against time as the independent variable.

When the concentrated infusion is dried, as by spray drying, to recover the soluble coffee solids in the form of particles of powder, the amount of heat which must be supplied to the drying operation to effect evaporation of the large quantities of water vaporized is substantial. For example, when the extract liquor contains 25% $01- ubles, the drier must evaporate three pounds of water for each pound of soluble coffee powder produced. An increase in the concentration of soluble coffee solids in the draw-off is desirable as it will permit decreased handling cost and greater throughput with existing driers i.e. production of larger amounts of soluble coffee powder per pound of water evaporated in the drier.

High draw-off concentration permits attainment of soluble coffee powder characterized by desirably darker color, more desirable particle size, and greater retention of volatile flavors or aroma. When, in prior art processes, attempts have been made to increase the soluble content of the draw-off to concentrations above 25% 30%, it is found that this can only be accomplished at the expense of consumer acceptance. Increasing the number of percolators has been found to be of no avail, since a larger number of percolators does not permit attainment of any significantly higher concentrations. Use of higher temperature feed water does yield an extract containing more solubles, but the various. severe reactions occurring at the higher temperatures, e.g., autoclaving and hydrolysis, give to the soluble coffee an undesirable flavor, taste, and aroma and results in undesirable' consumer reaction to coffee beverage made from the soluble product. Furthermore, in the prior art processes, when ground roasted coffee is extracted under conditions which give high concentrations, the amount of unrecovered soluble solids may be high. This represents undesirable loss resulting directly from excessive heat treatment of otherwise recoverable soluble solids, with attendant impairment of quality and consumer acceptance.

It is an object of this invention to extract solubles from coffee under conditions permitting attainment of high concentration of solubles in the draw-off. A second object of this invention is to obtain soluble coffee powder having a high level of consumer acceptance, a highly desirable flavor, and darker color. A further object of this invention is to obtain a better quality (i.e better flavor) soluble coffee than obtained by the prior art. Other objects will be apparent to those skilled-in-the-art on inspection of the following description and accompanying drawings.

In accordance with this invention, an extract of highly concentrated coffee solids is obtained by countercurrent extraction in a plurality of stages, there being at least a three section extraction system including a cold section, a hot section, and a cooling section. Each of these sections is characterized and defined by the temperatures prevailing therewithin as hereinafter described in detail.

The coffee extracted will be roasted coffee. While Whole beans may be treated, best results are attained with ground roasted coifee. This process is particularly adapted to percolators and accordingly, the ground roasted coifee may be packed in percolators, at least one percolator being included within each of the above-noted sections of the percolation train.

Preferably the charge extraction liquor admitted to the first percolator in the cold section will be water, but it may be a dilute aqueous extraction liquor containing soluble coffee from any convenient source. Feed water to the cold section may be at temperatures of 220 F. to 270 F., preferably 231 F. The extraction time (i.e. the time of residence of coffee grounds) in this section may range from to 60 minutes, preferably about minutes. The total extraction time is about 120-200 minutes, preferably 165 minutes for the overall cycle. The extraction liquor leaving the cold section may contain 0.2% to 4.0%, e.g. 2.0% solubles. The extracted coffee grounds blown down from the system may contain 0.2% to 4%, eg, 2% solubles. Operations in the cold section may be effected in a single percolator or in several percolators.

Before admission into the hot section of the percolation train, the enriched extract from the cold section will be heated to temperature above the outlet temperature of the cold section and preferably sufficiently to raise its temperature by about 40 F. to 65 F. As the extract enters the hot section, it will preferably be at temperature of 250 F. to 315 F., e.g. 294 F. When there are several percolators in this section, those containing the more spent coffee grounds may be operated at temperatures preferably at least as high as those in the same section containing the fresher coffee grounds. The time of contact between the extracting liquor and the beds of ground coffee in the hot section of the percolator train may be 40 minutes to 110 minutes, but preferably is about 75 minutes. Concentration of extract exiting this section may be 12% to Effluent from the hot section is admitted to the cooling section wherein it is cooled to temperature less than the outlet temperature of the hot section as it is contacted with fresher coffee grounds, the coffee grounds in the last percolator in this section being most fresh coffee. Immediately prior to and during its passage through the cooling section, the temperature of the infusion will be lowered by contact with the cooler coffee grounds and cooler percolators, by natural convection, by heat exchange, or by any one or more of these, so that the draw-off temperature is 175 F, to 200 F., prefer ably about 180 F. These conditions are obtained when the inlet temperature to the cooling section is 210 F.- 270 F., preferably about 210 F., and accordingly the effiuent from the hot section will have been cooled to these desired temperatures.

Extraction time in the cooling section may be minutes to 50 minutes, preferably about 42 minutes. The concentration of solubles in the effluent or draw-off from the cooling section may be as high as 35% to 45%, e.g. 41.3% which may represent a yield of 28%33%, e.g. 30%.

Figure 2 shows in diagrammatic form, the preferred ranges of temperature in the several sections of the percolation train. Along the bottom of the graph are plotted coffee stages which represent a time base according to which coffee is admitted to the system at a point corresponding to the left end of the time base, passes through the system, and leaves the system at a point corresponding to the right end of the graph. Aqueous extraction liquor, passing countercurrent to the coffee, enters the system at a point corresponding to the right end of the time base, passes through the system, and leaves the system at a point corresponding to the left end of the graph. The vertical coordinates indicate the temperature prevailing within the system. No particular significance is to be attributed to the specific times indicates for each of the sections; the time of extraction in each section may vary as hereinbefore indicated.

Because of the semi-continuous nature of the process, it will also be apparent to thoseskilled-in-the-art, that the temperatures in a given percolator and in each section will vary from time to time. For example, when a percolator containing fresh coffee grounds is placed on stream, the temperature in that percolator will be lower than it will be after the infusion from the hot section has been passing therethrough for some period of time. Accordingly, the plotted temperatures are those prevailing just prior to the time when the last percolator is blown down. Similarly, temperatures referred to elsewhere in this specification are also noted just prior to blow down.

During operation of the process, water will be admitted at temperature corresponding to the right end of the band of the graph of Fig. 2. It will be heated during its passage through the percolation train to the higher temperatures falling within the range bounded by the center of the band corresponding to the hot section of the percolation train. Subsequently the infusion will cool within the limits defined by the left end portion of the band, and the draw-off temperature of the infusion will be F.-200 F. as shown by the left end of the band.

The concentrated extract may be passed to a spray drier to evaporate Water therefrom. Spray drying of the extract provides a soluble coffee powder having a desirably darker color.

The soluble coffee powder prepared according to this process is found to be highly acceptable to the consumer even when the concentration in the draw-off liquor from which it is prepared is as high as e.g. 41%45%. It is characterized by desirable flavor and aroma and by the complete absence of those attributes generally resulting from excessive autoclaving or hydrolysis.

In order to illustrate the process, a preferred method of operation will be described in connection with the attached drawing, Fig. 1 of which illustrates a flow sheet of one embodiment according to which the process may be conducted. It will be understood by those skilledin-the-art that various modifications and changes may be made and that the attached drawings and the following description are illustrative only.

In Fig. 1 of the drawing, a plurality of percolators or extraction columns 10, 11, 12, 13, 14, and 15 are shown. Each percolator contains therewithin a screen (not shown) at the bottom thereof and a suitable screening device (also not shown) positioned in the upper part of the percolator whereby coffee is prevented from being carried out of the bed by the upflowing extraction liquor. Each percolator has at its upper end, a charge line 16, 17, 18, 19, 20 and 21, schematically shown, through which fresh charge coffee may be admitted to the percolator. The lower portion of each of the percolators is fitted with a coffee discharge or blow down line having a suitable blow down valve 42, 43, 44, 45, 46, or 47 through which coffee may be removed from the column when the appropriate blow down valve is opened.

Each percolator has a liquid inlet line 23, 24, 25, 26, 27, and 28 leading to the lower portion thereof. Each of the percolators is also fitted with a liquid outlet line leading from the top thereof. The outlet line from each percolator connects directly with the inlet line to the next succeeding percolator, whereby as liquid flows respectively through percolators 10, 11, 12, 13, 14 and 15, it passes through lines 23, 24, 25, 26, 27, 28 and is discharged from the system through line 41.

Each percolator is fitted with a heat exchanger 29, 30, 31, 32, 33 and 34, which may be an intracolumnar heat exchanger but preferably it will be positioned in the liquid inlet lines just before they enter the percolators. Each heat exchanger is provided with a heat exchange fluid line 35, 36, 37, 38, 39 and 40 through which appropriate heat exchange medium, e.g. cooling water or steam as hereinafter described, may be passed to modify the temperature of liquid admitted to the percolator. During a particular sequence of operations some of the heat exchangers may not be employed. It will'be understood that although the drawing shows a system containing six percolators, the number may be varied depending upon the prevailing conditions.

Example I In typical operation of the process according to one embodiment, extraction of coffee solubles was efiected in the six-column system set forth in Fig. 1 of the drawing. Each column was originally charged with 185 pounds of ground, roasted, blended coffee.

It will be apparent to those skilled-in-the-part that when starting up such a system, a certain period of time is required to bring the system to equilibrium i.e. to at tain steady operating conditions. Under conditions which prevail during steady operation of the process, feed water admitted through line 23 at pressure of about 200 psig. was heated by steam from line 35 in heat exchanger 29 to 231 F. This water was admitted to the bottom of percolator 10, which in this embodiment, comprises the first percolator of the cold section of the percolation train. The coffee grounds contained within percolator were nearly spent coifee grounds, which had had the major portion of their solubles extracted therefrom. The coflee grounds in this percolator (and in each of the subsequent percolators herein described) were contacted with extraction liquor for total period of about 165 minutes between filling and blow down. The charge liquor leaving percolator 10 contained approximately 2% by weight of soluble cofiee just before blown down.

The extract was passed through line 24 to percolator 11 of the percolator train. It was heated in heat exchanger 30 by steam from line 36 to temperature of 247 F. and then admitted to percolator 11. Here it passed upwardly through a bed of coffee grounds which were fresher i.e. which contained more solubles, than the coffee in percolator 10. Draw-off from the top of percolator 11 was passed through line 25 to heat exchanger 31, wherein it was heated by steam from line 37 to temperature of 294 F. This hot extraction liquor was passed upwardly through percolator 12 and left the same through line 26. Heating in heat exchanger 32, by steam from line 38, raised the temperature to 298 F. The heated liquor was thence passed upwardly through the bed of coffee in percolator 13.

Concentrated extract leaving percolator 13 was passed through line 27 to heat exchanger 33 wherein it was heated by steam from line 39 to 254 F. The extract was then contacted with coffee grounds in percolator 14, the efliuent from which in line 28 contained about 17.5% solubles. In this embodiment, the total time of contact of coffee with extraction liquor in the hot section, comprising percolators 12, 13 and 14, was 75 minutes.

Liquor leaving percolator 14 was passed through line 27 to the cooling section comprising percolator 15. Liquid leaving the hot section was permitted to cool by natural convection and accordingly heat exchanger 34 was not herein employed. Extraction liquor at 210 F. was passed upwardly through percolator 15. Here the upflowing extraction liquor contacted coffee grounds which were substantially fresh.

Draw-off in line 41 from percolator 15 was at temperature of 180 F. Total time of contact of coffee grounds with the extracting liquor in the cooling section of the percolation train of this example was 42 minutes. Concentration of solubles in the draw-off was 41.3%.

During the course of this example, the average drawoff factor, i.e. the ratio of weight of extract solution passed through a bed of ground coffee to the weight of ground coffee in the bed was 0.79. Concentration of solubles in the extraction liquor just before blow down, which number is an indication of the thoroughness of extraction, was 2%. Powdered coffee, produced by spray drying the draw-off infustion, had a desirably dark color.

Pressure in the several percolators was adequate to main tain liquid phase operations therewithin.

The dashed curve of Fig. 2 shows the temperature characteristics of this embodiment of the invention plotted as hereinbefore described. As shown in that curve, the feed water enters the cold section of the percolation train at 231 F.; it is heated to temperatures as high as 298 F. in the hot section; and it cools to 180 F. during its passage through the cooling section;

Although there is herein described a specific embodiment of this invention, it will be apparent to those skilled-in-the-art that various changes and modifications may be made thereto which come within the scope of this invention.

What is claimed is:

1. A coifee extraction process for producing concentrated coffee extract by contacting cofiee grounds countercurrently with an aqueous extraction liquor which comprises extracting hot nearly spent coffee grounds in a cold section of an extraction train with aqueous extraction liquor admitted thereto at about 220 F. to 270 F. whereby the temperature of said liquor is raised, withdrawing extraction liquor from said cold section at temperature higher than said inlet temperature, heating said withdrawn liquor 'to temperature above the outlet temperature of the cold section and to within the range of 250 F.-315 F., contacting said heated extraction liquor at this temperature in a hot section of the extraction train with coffee grounds fresher than those in said cold section, withdrawing extraction liquor from said hot section, contacting said withdrawn extraction liquor at about 210 F.270 F. in a cooling section with coffee grounds fresher than those in said hot section, and withdrawing from said cooling section concentrated extraction liquor at about F.200 F.

2. A coffee extraction process as claimed in claim 1 wherein the extraction liquor in said cooling section is cooled to 175 F.200 F. by natural convection during the extraction in the cooling section of the extraction train.

3. A coffee extraction process for producing concentrated coffee extract by contacting coffee grounds countercurrently with an aqueous extraction liquor which comprises extracting hot nearly spent coffee grounds in a cold section of an extraction train with aqueous extraction liquor admitted thereto at about 220 F.-270 F, withdrawing extraction liquor from said cold section at temperature higher than said inlet temperature, heat- :ing said withdrawn liquor to temperature about 40 .F.-65 F. above the outlet temperature of the cold section and to within the range of 250 F.3l5 F., contacting said heated extraction liquor at this temperature in a hot section of the extraction train with coffee grounds fresher than those in said cold section, withdrawing extraction liquor from said hot section, contacting said withdrawn extraction liquor at about 210 F.270 F. in a cooling section with coffee grounds fresher than those in said hot section, and withdrawing from said cooling section concentrated extraction liquor at about 175 F.-200 F.

4. A coffee extraction process for producing concentrated coffee extract by contacting coffee grounds countercurrently with an aqueous extraction liquor which comprises extracting hot nearly spent coffee grounds in :a cold section of an extractioon train with aqueous extraction liquor admitted thereto at about 220 F.270 F. whereby the concentration of soluble cofiee in said extraction liquor is raised to less than about 4% and whereby the temperature of said liquor is raised, withdrawing extraction liquor from said cold section at temperature higher than said inlet temperature, heating said withdrawn liquor to temperature above the outlet temperature of the cold section and to within the range of 250 F.-3l5 F., contacting said heated extraction liquor at this temperature in a hot section of the extraction train with coffee grounds fresher than those in said cold section whereby the concentration of soluble coffee in said extraction liquor is raised to about 12%30%, withdrawing extraction liquor from said hot section, contacting said withdrawn extraction liquor at about 210 F.270 F. in a cooling section with coffee grounds fresher than those in said hot section, and withdrawing from said cooling section extraction liquor at about 175 F.200 Ffihaving concentration of about 35%- 45% of soluble coffee the total time of extraction being 120-200 minutes.

5. A coffee extraction process for producing concentrated coffee extract by contacting coffee grounds countercurrently with an aqueous extraction liquor which comprises extracting hot nearly spentcotfeegrounds in a cold section of an extraction train for 1560 minutes With aqueous extraction liquor admitted thereto at about 220 F.270 F. whereby the temperature of said liquor is raised, withdrawing extraction liquor from said cold section at temperature higher than said inlet temperature, heating said withdrawn liquor to temperature above the outlet temperature of the cold section, and to within the range of 250 F.-315 F., contacting said heated extraction liquor at this temperature in a hot section of the extraction train for 40-110 minutes with coffee grounds fresher than those in said cold section, withdrawing extraction liquor from said hot section, contacting said withdrawn extraction liquor at about 210 F.-270 F. in a cooling section for 35-50 minutes with coffee grounds fresher than those in said hot section, and with- 8 drawing from said cooling section concentrated extraction liquor at about F.-200 F.

6. A coffee extraction process for producing concentrated coffee extract by contacting coffee grounds coun tercurrently with water which comprises extracting hot nearly spent coffee grounds in a cold section of an extraction train with water admitted thereto at about 231 F. whereby the temperature of said liquor is raised, withdrawing extraetion liquor from said cold section containingabout 2% by Weight of soluble coffee at tern- ;reraturc higher than said inlet temperature, heating said withdrawn liquor to temperature of about 294 F., contacting said heated extraction liquor at this temperature in a hot section of the extraction train with coffee grounds fresher than those in said cold section, withdrawing extraction liquor from said hot section containing about 17.5% by weight of soluble coffee, contacting said withdrawn extraction liquor at about 210 F. in a cooling section with coffee grounds fresher than those in said hot section, and withdrawing from said cooling section concentrated extraction liquor at about 180 F. halving concentration of about 41.3% of soluble coffee.

References Cited in the file of this patent UNITED STATES PATENTS 1,925,159 Wendt Sept. 5, 1933 2,410,157 Fredrickson Oct. 29, 1946 2,515,730 Ornfelt July 18, 1950 2,758,927 Chase Aug. 14, 1956 

1. A COFFEE EXTRACTION PROCESS FOR PRODUCING CONCENTRATED COFFEE EXTRACTED BY CONTACTING COFFEE GROUNDS COUNTERCURRENTLY WITH AN AQUEOUS EXTRACTION LIQUOR WHICH COMPRISES EXTRACTING HOT NEARLY SPENT COFFEE GROUNDS IN A COLD SECTION OF ANEXTRACTION TRAIN WITH AQUEOUS EXTRACTION LIQUOR ADMITTED THERETO AT ABOUT 220*FF. TO 270* F. WHEREBY THE TEMPERATURE OF SAID LIQUOR IS RAISED, WITHDRAWING EXTRACTION LIQUOR FROM SAID COLD SECTION AT TEMPERATURE HIGHER THAN SAID INLET TEMPERATURE, HEATING SAID WITHDRAWN LIQUOR TO TEMPERATURE ABOVE THE OUTLET TEMPERATURE OF THE COLD SECTION AND TO WITHIN THE RANGE OF 250* F.-315*F., CONTACTING SAID HEATED EXTRACTION LIQUOR AT THIS TEMPERATURE IN A HOT OF THE EXTRACTION TRAIN WITH COFFEE GROUNDS FRESHER THAN THOSE IN SAID COLD SECTION, WITHDRAWING EXTRACTION LIQUOR FROM SAID HOT SECTION, CONTACTING SAID WITHDRAWN EXTRACTION LIQUOR AT ABOUT 210*F.-270*F. IN A COOLING SECTION WITH COFFEE GROUNDS FRESHER THAN THOSE IN SAID HOT SECTION, AND WITHDRAWING FROMSAID COOLING SECTION CONCENTRATED EXTRACTION LIQUOR AT ABOUT 175*F.-200*F. 